Black Mould in New Zealand
That dark patch might be toxic Stachybotrys — or one of a dozen look-alikes. Only the lab knows for sure.
See your testing optionsDon't Guess What You're Breathing
"Black mould" is one of the most-searched home health concerns in New Zealand — and for good reason. Our damp, temperate climate lets mould thrive year-round, from Auckland to Invercargill. But here's what most people don't realise: the dangerous "toxic black mould" you've read about is just one of many dark moulds, and they are impossible to tell apart by eye. Getting it identified is the step that decides everything that follows.
Scaada NZ provides black mould identification, professional mould assessment, and laboratory testing by qualified mould analysts throughout New Zealand. Courier a sample to our Hamilton lab from anywhere in the country, or have one of our assessors attend on site.
Two Ways to Find Out for Certain
Most people start with a post-in lab test — it's the cheapest way to get a definitive answer. If the problem is bigger, or you need it documented for insurance, tenancy or a sale, an on-site assessment digs deeper.
Post-in lab test
You take the sample — we identify it under the microscope.
$250 + GST per sample
Sample kit included · qualified-analyst report in 3 business days
- We post you a tape-lift kit with simple instructions
- Genus identified and spore density quantified (ASTM D7658-17)
- Confirms whether it's Stachybotrys or a look-alike
- Defensible report for landlords, insurers and your GP
On-site assessment
We come to you for the full picture, including the moisture source.
from $800 + GST
Multi-area sampling · moisture mapping · IICRC S520 report
- Air & surface sampling across the property
- Moisture readings that locate the water source, not just the mould
- Best for health symptoms, bigger areas, or insurance & legal matters
- Carried out nationwide by us or our trusted assessor network
1 · We post your kit
Tell us your region and we send a tape-lift kit with step-by-step instructions.
2 · Take a sample, courier it back
Lift a sample from the affected area and send it to our Hamilton lab overnight.
3 · Get your report
A clear result from our qualified mould analysts in 3 business days — what it is, and what to do next.
Not sure which fits? Call or text 022 315 1171, or see the full sample submission process.
What "Black Mould" Actually Is
When people say "black mould" or "toxic black mould", they almost always mean Stachybotrys chartarum. It needs sustained moisture to grow (water activity above 0.90) and feeds on cellulose-rich materials — plasterboard, timber, paper and fabrics. Because it is hydrophilic, finding it is a strong signal of prolonged water damage or an ongoing leak, not just high humidity.
What makes it a genuine concern is its production of Trichothecene mycotoxins, which interfere with protein, DNA and RNA synthesis. The spores aren't readily airborne, but the mycotoxins can be — so exposure can occur even when the growth looks contained behind a wall or under a floor.
Is It Actually Black Mould? Meet the Line-Up
Every mould below can read as a dark patch on a wall. Under the microscope they are unmistakable — and they carry very different health risks and remediation needs. This is exactly why a visual guess isn't enough. All images are real microscopy from the Scaada NZ laboratory.
Stachybotrys
True "toxic black mould." Needs sustained water damage to grow and produces trichothecene mycotoxins.
Aspergillus
Tiny respirable spores (<3 μm) that settle deep in the lungs. Linked to Aspergillosis and CIRS.
Penicillium
Common and fast-spreading. Some strains produce mycophenolic acid, a potent immunosuppressant.
Cladosporium
One of the most common indoor moulds. Usually lower-risk — but you can't assume that by eye.
Ulocladium / Alternaria
A strong asthma trigger, especially in children, and a heavy water-damage indicator indoors.
Chaetomium
A water-damage mould whose mycotoxins are highly allergenic even at low doses.
Same colour, very different problem. Only laboratory microscopy — methods such as ASTM D7658-17 — can tell you which one is on your wall and what it means for your health.
The Health Risks — and Who's Most at Risk
Health effects depend on the genera, the concentration, how long you're exposed, and how susceptible you are. They range from mild irritation to serious illness.
Allergic & respiratory effects
Sneezing, itchy eyes, skin irritation, rhinitis and sinusitis — through to airway inflammation, asthma flare-ups and a persistent cough.
Mycotoxin exposure
Stachybotrys trichothecenes and Chaetomium chaetoglobosins can cause acute and chronic effects.
Immune sensitisation
Chronic exposure to (1→3)-β-D-glucans can build toward Hypersensitivity Pneumonitis.
Most vulnerable: children and infants, the elderly, immunocompromised people, those with asthma or other respiratory conditions, and pregnant individuals. Read more on mould exposure and health effects.
Found something dark and you're not sure?
Send us a sample from anywhere in New Zealand, or book an on-site assessment. Either way you get a clear report from qualified mould analysts telling you exactly what it is and what to do next.
What the Guidance Says (BRANZ & Healthy Homes)
You don't have to take our word for it — New Zealand's building and tenancy guidance all points the same way: mould is a moisture problem first.
- BRANZ (Building Research Association of NZ) is clear that indoor mould is driven by excess moisture, and that lasting control comes from fixing the source — ventilation, heating and stopping water ingress — not from wiping the surface.
- Healthy Homes Standards 2019 require rental properties to meet minimum standards for heating, insulation, ventilation, moisture ingress and drainage, and draught-stopping — the exact conditions that keep mould from taking hold.
- NZS 4303:1990 recommends keeping indoor relative humidity below 60%. Readings consistently above that support mould germination even on surfaces that look dry.
A laboratory report gives you objective, documented evidence — the kind that carries weight with a landlord, an insurer, a remediation contractor or your GP.
Found Suspected Black Mould? Do This
Before you reach for the bleach — the order of operations matters. Getting it wrong spreads the problem.
- Don't disturb it. Scrubbing or dry-brushing releases spores (and, with Stachybotrys, mycotoxins) into the air. Leave it until it's assessed.
- Don't just bleach it. Bleach hits surface growth only — the hyphae penetrate porous materials and regrow, and you still won't know the genera.
- Get it tested. Collect a surface sample with a tape-lift kit (we send one with instructions), or book a professional on-site assessment with moisture readings.
- Fix the moisture source. Leaks, condensation, rising damp, poor ventilation — without addressing the water, mould returns after any clean-up.
- Use qualified remediators for bigger jobs. For areas over 1 m², remediation to IICRC S520 standards is recommended, with a Post-Remediation Verification to confirm it worked.
Read why bleach (and vinegar) don't kill mould — with lab samples taken after DIY clean-ups.
How We Confirm It
Our qualified mould analysts and occupational hygienists identify exactly what's present and how serious it is, then report it against the IICRC S520 condition ratings.
Surface sampling
A tape-lift captures a 4 cm² sample with spores and hyphae intact, analysed under microscopy (ASTM D7658-17) to identify the genera and tell active growth from settled spores blown in from elsewhere.
Air sampling
Spore-trap cassettes measure airborne structures, compared against an outdoor reference sample taken the same day to show whether indoor levels are genuinely elevated.
Moisture & environment
Non-invasive moisture readings, temperature and relative humidity locate the water driving growth — not just the mould itself.
Condition 1 · Normal
Typical of a healthy indoor environment. No remediation required.
Condition 2 · Settled spores
Elevated spores settled from elsewhere. Cleaning advised; find the source.
Condition 3 · Active growth
Confirmed colonisation. Professional remediation recommended.
Black Mould FAQ
Is black mould dangerous in New Zealand homes?
Stachybotrys chartarum ("black mould") produces Trichothecene mycotoxins that can inhibit protein, DNA and RNA synthesis. Health effects range from allergic reactions to serious respiratory conditions, particularly for vulnerable populations. However, not all dark mould is Stachybotrys — professional laboratory testing is the only reliable way to confirm the genera and assess the actual risk.
How do I test for black mould in my house?
You can collect a surface sample yourself using a tape lift kit (contact us and we'll send one with instructions), or arrange a professional on-site assessment for comprehensive evaluation. Samples are examined under microscopy using ASTM D7658-17 methodology to identify the specific mould genera present. Air sampling can also assess whether spore levels are elevated indoors compared to outside.
What should I do about black mould in my rental property?
Under the Healthy Homes Standards, landlords must address moisture and ventilation. If you find suspected black mould: don't disturb it, notify your landlord in writing, and consider professional testing. A laboratory report documents the genera and contamination level, providing objective evidence for discussions with your landlord or property manager.
What does black mould look like?
Stachybotrys typically appears as dark greenish-black patches with a slimy or wet texture when actively growing. However, Aspergillus, Penicillium, Cladosporium, and Ulocladium can all appear dark or black. Visual identification is unreliable — laboratory microscopy is required to confirm genera and assess health risk.
Can I remove black mould myself?
For small areas (under 1 m²) of surface mould, careful cleaning with appropriate products may be sufficient — but you should still get it tested first to know what you're dealing with. For areas larger than 1 m², or if mould keeps returning, professional remediation is recommended. Stachybotrys in particular should not be disturbed without proper containment as this releases mycotoxins into the air.
Order a Test Kit or Ask Us
Tell us about your situation — to order a test kit ($250 ex GST), choose "Request a test kit" below and we'll post one out.
You'll talk to a real mycologist, not a call centre · No obligation · We reply within 1 business day